According to the prior art techniques, metal cabinets are constructed by assembling steel sheets in an overlapping fashion to form a box-like arrangement. These sheets are then spot welded or otherwise joined to produce a permanently joined structure.
In certain situations, an outer box is first assembled by arranging metal sheets in an overlapping fashion to form a box-like structure. This structure is made permanent by welding, riveting, or otherwise joining the outer box components in their assembled relation. At the time of joining these components, care must be taken to maintain the desired arrangement of plates and dimensions of the cabinet. If necessary, stiffeners or other reinforcement can be added to the inside or outside of the outer box structure.
After the outer box is permanently assembled, an inner box can be assembled by arranging metal or plastic sheets in an overlapping fashion to form a box-like arrangement having smaller dimenisons than the outer box. Then, after adding any insulation, fillers, fire resistant components or other materials to the inside of the outer box, the inner box joined by welding, adhesively bonding or other suitable joining methods, and is placed inside of the outer box.
To finish construction of the cabinet, the inner box is connected to the outer box. For certain cabinets, such as file cabinets, this is accomplished by mating the inner and outer box metal panels and spot welding them together. In certain situations, an adhesive, foam, or other medium capable of adhering to the inner and outer box members is introduced and allowed to cure or polymerize.
One particular industry which uses a variation of the outer box/inner box cabinet fabrication is the refrigeration industry. Refrigeration cabinets are constructed of an inner box section positioned within an outer box section and dimensioned to define an approximately 2" space between the box sections. This 2" space is then filled with an insulating medium, such as a relatively high density polyurethane foam, which is formed in situ between the box sections when they are positioned within supporting molds.
An outer box section is first assembled by assembling steel sheets in an overlapping fashion to form a box-like arrangement. Thereafter, the sheets are spot welded so as to be retained in an assembled relation. An inner box section is then fabricated in the same manner as the outer box section. Thereafter, the outer box section is positioned within a rigid steel jig which defines a cavity by steel side walls against which the outer box section is snugly positioned. It is important to provide high strength lateral support for the walls of the outer box section for reasons which will be explained below.
The inner box section is subsequently positioned within the outer box section and a high strength mold or jig is positioned within the cavity defined by the inner box section. When the two box sections are thus positioned, movement of either the outer box section outward or the inner box section inward is completely prevented. Next, polyurethane foam forming materials are injected into the space between the inner and outer box sections.
This high density polyurethane foam expands and exerts pressure against the inner and outer box sections. The forces which are generated by the foam forming materials against the inner and outer box sections are very substantial and in the absence of a mold jig having very high strength support walls, the stainless steel sheet materials forming the inner and outer box sections would buckle inwardly and outwardly respectively. The forces provided by the foam forming materials are so high that they would substantially distort the shape of the box sections.
Hence, a mold jig is required that has walls which can provide uniformly distributed support over all surfaces of the inner and outer steel sheet metal members of the refrigeration cabinet during the time period that the insulating foam material is expanding. Then, since movement of the box sections is prohibited, the foam expands to fill the cavity between the sections. Also, the foam provides thermal insulation of one section from the other.
The techniques thus far discussed for producing refrigeration cabinets utilize the steps of assembling and spot welding the steel plates on a separate jig, and require careful attention to the dimensions of the unit during welding. In addition, storing the inner and outer boxes prior to the fabrication of the refrigerator requires a great amount of space, which space is not always readily available and which is costly to provide.
I have invented an apparatus, method and system which avoids these disadvantages while reducing the cost of production of the refrigeration cabinet.